JPH0931199A - Organosiloxane copolymer and preparation thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel organosiloxane copolymer which has excellent low-temp. properties, heat resistance, temp.-viscosity characteristics, and compatibility with various lubricants and is useful as a raw material particularly for cosmetics, greases and the like. SOLUTION: This organosiloxane copolymer is represented by the formula [wherein R<1> represents a monovalent hydrocarbon group; R<2> and R<3> each independently represent a monovalent hydrocarbon group or an alkyl group with hydrogen atoms being partially or entirely substd. by a halogen atom; A represents a hydrogen atom or an organosilyl group represented by the general formula -SiR<4> (R<4> independently represents a hydrogen atom or a monovalent org. group, provided that at least one R<4> represents a monovalent org. group); a is an integer of 4 or more, b is an integer of 2 or more; and c is an integer of 0 or more].

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel organosiloxane copolymer having a trimethylsiloxy group and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, polysiloxanes have been produced by an equilibration reaction of cyclic polysiloxanes and linear polysiloxanes or a cohydrolysis condensation reaction of chlorosilanes. However, in these methods, the cleavage / polymerization reaction proceeds at random. Therefore, these methods cannot control the structure of the obtained polysiloxane, and cannot manufacture the organosiloxane copolymer containing a predetermined amount of trimethylsiloxy groups. Therefore, a branched polysiloxane having a trimethylsiloxy group in its side chain has not yet been known.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a novel organosiloxane copolymer having a trimethylsiloxy group bonded to a silicon atom as a side chain, and a method for producing the same.

[0004]

The first aspect of the present invention is to provide the following general formula (1):

[0005]

Embedded image [Wherein R ¹ is a monovalent hydrocarbon group, R ² and R ³ are independently a monovalent hydrocarbon group or an alkyl group in which some or all of hydrogen atoms are substituted with halogen atoms, and A is Hydrogen atom or the following general formula: —SiR ⁴ (In the formula, R ⁴ is independently a hydrogen atom or a monovalent organic group.
However, at least one R ⁴ is a monovalent organic group), a is an integer of 4 or more, b is an integer of 2 or more, and c is an integer of 0 or more. Yes] is an organosiloxane copolymer. The second aspect of the present invention is the following formula (2):

[0006]

Embedded image A cyclotrisiloxane represented by the following general formula (3):

[0007]

[Chemical 6] (Wherein R ² and R ³ are independently a monovalent hydrocarbon group or a halogenated alkyl group), together with a cyclotrisiloxane represented by the following general formula (4): R ¹ (R ⁵ R ⁶ SiO) _n Li (4) (In the formula, R ¹ is a monovalent hydrocarbon group, R ⁵ and R ⁶ are independently a monovalent hydrocarbon group or a halogenated alkyl group, and n is an integer of 0 or more.) The ring-opening polymerization is carried out in the presence of a lithium compound represented by the following formula, and then the reaction mixture is treated with an acid or the following general formula (5): XSiR ⁴ (5) (wherein, X is a halogen atom and R ⁴ is independently A hydrogen atom or a monovalent organic group, provided that at least one R ⁴
Is a monovalent organic group) is a method for producing the above organosiloxane copolymer, which comprises the step of terminating the above ring-opening polymerization by adding an organohalosilane. Hereinafter, the present invention will be described in detail.

Organosiloxane Copolymer The copolymer of the present invention is represented by the above general formula (1) and has the following formula:

[0009]

[Chemical 7] The unit represented by (hereinafter referred to as D ¹ unit), the following formula:

[0010]

Embedded image The unit represented by (hereinafter referred to as D ² unit) and the following formula:

[0011]

Embedded image In unit represented (hereinafter, D of ³ units) and recurring units of at least one unit selected from the group consisting of,
Depending on the case, in addition to these units, the following formula:

[0012]

Embedded image (In the formula, R ² and R ³ are the same as above), which is a copolymer having a repeating unit as a unit (hereinafter referred to as D ⁴ unit).

Typical examples of such copolymers include the following formulas: R ¹ -D ¹ _b -A, R ¹ -D ² _b -A,
R ¹ -D ³ _b -A, R ¹ -D ¹ _d D ² _d -A, R ¹ -D
¹ _d D ³ _d -A, R ¹ -D ² _d D ³ _d -A, R ¹ -D ¹
_e D ² _e D ³ _e −A, R ¹ −D ¹ _b D ⁴ _f −A, R ¹ −
D ² _b D ⁴ _f -A, R ¹ -D ³ _b D ⁴ _f -A, R ¹ -D
¹ _d D ² _d D ⁴ _f −A, R ¹ −D ¹ _d D ³ _d D ⁴ _f −
A, R ¹ -D ² _d D ³ _d D ⁴ _f -A, R ¹ -D ¹ _e D ²
_e D ³ _e D ⁴ _f −A (In the formula, R ¹ , A, D ¹ , D ² , D
³ , D ⁴ and b are the same as above, and d, e and f are 1
The above-mentioned integers, preferably 2 to 150) are listed, and these may be random copolymers or block copolymers.

In the general formula (1), examples of the monovalent hydrocarbon group represented by R ¹ include an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, an alkenyl group and a (meth) acryloyloxypropyl group. .

Examples of the alkyl group for R ¹ include, for example,
Methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group,
Number of carbon atoms such as neopentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, dodecyl group, etc.
To 12 alkyl groups, more typical of which are C1-8 methyl, propyl, hexyl and octyl groups.

Examples of the cycloalkyl group represented by R ¹ include cycloalkyl groups having 3 to 12 carbon atoms such as cyclopentyl group, cyclohexyl group and cycloheptyl group, and more typical ones are those having 5 carbon atoms. To cyclopentyl group, cyclohexyl group, and cyclooctyl group.

Examples of the aryl group of R ¹ include, for example,
Examples thereof include aryl groups having 6 to 18 carbon atoms such as phenyl group, tolyl group, xylyl group, naphthyl group, and biphenylyl group. Further, typical ones are phenyl group having 1 to 12 carbon atoms, tolyl group, naphthyl group. Is.

Examples of the aralkyl group represented by R ¹ include aralkyl groups having 7 to 12 carbon atoms such as benzyl group, phenylethyl group, phenylpropyl group, and methylbenzyl group. Number of atoms 7
To benzyl and phenylpropyl groups.

Examples of the alkenyl group represented by R ¹ include alkenyl groups having 2 to 12 carbon atoms such as vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group, isobutenyl group, hexenyl group and cyclohexenyl group. And more typical ones have 2 to 6 carbon atoms.
Of vinyl group, allyl group and hexenyl group.

The monovalent hydrocarbon group for R ² or R ³ is
Examples thereof are the same as those for R ¹ . Especially R ² or R ³
Suitable monovalent hydrocarbon groups as are a methyl group, a phenyl group and a vinyl group. Examples of the halogen-substituted alkyl group for R ² or R ³ include, for example, chloromethyl group, 2-bromoethyl group, 3-chloropropyl group, 3,3,3-trifluoropropyl group, 3,3,4,4,5. , 5, 6, 6,
Examples thereof include halogen-substituted alkyl groups having 1 to 6 carbon atoms such as 6-nonafluorohexyl group.

The organosilyl group of A has the following general formula: -SiR ⁴ (wherein, R ⁴ is independently a hydrogen atom or a monovalent organic group.
However, at least one R ⁴ is a monovalent organic group).

Examples of the monovalent organic group represented by R ⁴ include the same monovalent hydrocarbon groups and halogen-substituted alkyl groups as those described above for R ² or R ³ , as well as a part of hydrogen atoms bonded to carbon atoms or Other substituted monovalent hydrocarbon groups which are wholly substituted with halogen atoms, cyano groups and the like, for example, chlorophenyl group, fluorophenyl group, cyanoethyl group and the like can be mentioned.

In the general formula (1), a is an integer of 4 or more, preferably 10 to 540, b is an integer of 2 or more,
It is preferably an integer of 5 to 270, c is an integer of 0 or more, and preferably an integer of 3 to 450. The average molecular weight of the copolymer of the present invention is 800 to 200,000, preferably 2,000 to 100,000.

Specific examples of the copolymer of the present invention include, but are not limited to, those represented by the following formula.

[0025]

Embedded image (Where a and b are a ≧ 4, b ≧ 2 and 6 ≦ a + b ≦
It is an integer that satisfies 2,300)

[0026]

[Chemical 12] (In the formula, Bu is a butyl group, and a and b are a ≧ 4,
b is an integer that satisfies 2 and 6 ≦ a + b ≦ 2,300)

[0027]

Embedded image (In the formula, Bu is a butyl group, Ph is a phenyl group, and a, b, and c are a ≧ 4, b ≧ 2, 0 ≦ c ≦ 1,0.
00 and 6 ≦ a + b + c ≦ 2,300)

[0028]

Embedded image (In the formula, Bu is a butyl group, and a, b, and c are a ≧
4, b ≧ 2, 0 ≦ c ≦ 1,000 and 6 ≦ a + b + c ≦
It is an integer that satisfies 2,300)

[0029]

Embedded image (In the formula, Bu is a butyl group, and a, b, and c are a ≧
4, b ≧ 2, 0 ≦ c ≦ 1,000 and 6 ≦ a + b + c ≦
It is an integer that satisfies 2,300)

Method of Producing Organosiloxane Copolymer The method of the present invention comprises the step of adding the cyclotrisiloxane of the formula (2), optionally together with the cyclotrisiloxane of the formula (3), to the formula (4). Ring-opening polymerization in the presence of the lithium compound, and reacting the obtained reaction product with an acid or the organohalosilane of the general formula (5).

(I) Cyclotrisiloxane of the general formula (3) The cyclotrisiloxane of the general formula (3) can be obtained by adding the following general formula to the copolymer of the present invention: —Si (R ² ) (R ³ ) O— ( In the formula, R ² and R ³ are the same as the above), and are used as necessary to introduce a unit. R ² and R ^{3 in} the general formula (3) are the same as above.

Specific examples of the cyclotrisiloxane of the general formula (3) include hexamethylcyclotrisiloxane, hexaethylcyclotrisiloxane, hexaphenylcyclotrisiloxane, hexavinylcyclotrisiloxane, 1,3,5- Trimethyl-1,3,5-triphenylcyclotrisiloxane, 1,3,5-trimethyl-1,3,5-trivinylcyclotrisiloxane,
1,3,5-trimethyl-1,3,5-tris (3,3
3,3-trifluoropropyl) cyclotrisiloxane, 1,3,5-trimethyl-1,3,5-tribenzylcyclotrisiloxane and the like can be mentioned.

The amount of the cyclotrisiloxane of the general formula (3) used is 0 to 100 mol, preferably 0.1 to 50 mol, per 1 mol of the cyclotrisiloxane of the formula (2).

(Ii) Lithium Compound The lithium compound used in the production method of the present invention is represented by the general formula (4), and ring-opening polymerization of the cyclotrisiloxane of the general formula (2) or the cyclotrisiloxane of the general formula (3). Acts as a catalyst for the reaction. R ^{1 in the} general formula (4) is the above R ¹
Is the same as Examples of the monovalent hydrocarbon group and halogen-substituted alkyl group for R ⁵ and R ^{6 in} the general formula (4) include those described above for R ²
Alternatively, those similar to R ³ can be mentioned. N in general formula (4)
Is an integer of 0 or more, preferably an integer of 0-10.

Specific examples of such a lithium compound include, for example, methyllithium, n-butyllithium and s.
alkyl lithium such as ec-butyl lithium and tert-butyl lithium; vinyl lithium, allyl lithium,
Alkenyllithium such as hexenyllithium; aryllithium such as phenyllithium and naphthyllithium; organolithium compounds such as aralkyllithium such as benzyllithium and phenylethyllithium; lithium trimethylsilanolate, lithium dimethylvinylsilanolate, lithium diphenylmethylsilanolate. lithium salts of organosilane and the like; the following general _{^{formula: R 7 - (Me 2 SiO}} ) 3 -Li ( wherein, R ⁷ is a methyl group or a butyl group, Me is a methyl group) organosilane represented by Examples thereof include lithium salts of polysiloxane.

As such a lithium compound, for example, a compound of the general formula (4) in which n is 0 may be a commercially available product, and n is 1.
The above is easily obtained by reacting an organosilane having one silanol group, an organopolysiloxane having an silanol group at one end of the molecular chain or an organocyclopolysiloxane with the above lithium compound having n = 0. be able to.

(Iii) Acid or Organohalosilane In the production method of the present invention, the above-mentioned cyclotrisiloxane is subjected to ring-opening polymerization, and an acid or an organohalosilane of the general formula (5) is added to the reaction mixture. The polymerization reaction is stopped. When the above-mentioned acid is used to terminate the polymerization reaction, a copolymer in which A in the general formula (1) is a hydrogen atom can be obtained, and when an organohalosilane is used, A is the above-mentioned organo A copolymer having a silyl group can be obtained. Further, when the organohalosilane is an organohydrogenhalosilane, A is a group having a hydrogen atom bonded to a silicon atom. Therefore, various functional groups can be introduced through the A by a hydrosilylation reaction into the copolymer of the present invention having the group A containing a hydrogen atom bonded to a silicon atom. In particular, the copolymer in which the functional group thus introduced is a reactive group is useful as a macromonomer.

Examples of the acid include formic acid, acetic acid,
Organic acids such as propionic acid, citric acid, benzoic acid; carbonic acid,
Examples thereof include inorganic acids such as hydrochloric acid and sulfuric acid.

Examples of the above-mentioned organohalosilane include trimethylchlorosilane, dimethylchlorosilane,
Vinyldimethylchlorosilane, (3-acryloyloxypropyl) dimethylchlorosilane, (3-methacryloyloxypropyl) dimethylchlorosilane, (4-styryl) dimethylchlorosilane, dimethylhydrogenchlorosilane, trimethylbromosilane, dimethylbromosilane, vinyldimethylbromosilane, (3-acryloyloxypropyl) dimethylbromosilane, (3
-Methacryloyloxypropyl) dimethyl bromo silane, (4-styryl) dimethyl bromo silane, dimethyl hydrogen bromo silane, etc. are mentioned.

The amount of the above-mentioned acid or organohalosilane used is usually 1 to 5 per 1 mol of the lithium compound used.
The molar amount is preferably 1 to 2 mol.

According to the production method of the present invention, the reaction such as the ring-opening polymerization described above proceeds even without using a reaction solvent, but the reaction can be performed more favorably in an organic solvent and the yield of the present invention is good. A copolymer can be obtained.

Examples of the organic solvent include diethyl ether, tetrahydrofuran, 1,4-dioxane,
Examples include ether reaction solvents such as diethylene glycol dimethyl ether; aprotic solvents such as dimethyl sulfoxide and dimethylformamide; hexane; decane; benzene; toluene; organic solvents such as xylene. These are used alone or in combination of two or more. be able to. In particular, a reaction solvent having a low polarity such as toluene can be allowed to proceed better by combining it with a reaction solvent having a high polarity such as tetrahydrofuran or dimethylformamide. The amount of the reaction solvent used is preferably such that the concentration of the cyclotrisiloxane becomes 5 to 90% by weight.

The temperature of the above ring-opening polymerization reaction is -20 to 5
The temperature may be about 0 ° C., and the polymerization reaction proceeds well by setting in such a temperature range. Moreover, when using the said solvent, the temperature below the boiling point of a solvent is preferable. The reaction time may be about 10 minutes to 24 hours. Further, it is preferable that the reaction mixture is stirred and aged for a certain period of time after the addition of the above-mentioned acid or organohalosilane. The aging temperature may be about 0 to 50 ° C., and the aging time may be about 5 minutes to 5 hours.

The thus-obtained copolymer of the present invention can be used as a raw material for cosmetics and grease, in addition to its known use as a silicone oil.

[0045]

Example 1 The inside of a four-necked flask was replaced with dry nitrogen gas, and 30 g (80 mmol) of cyclotrisiloxane of the formula (2) and 100 g of tetrahydrofuran were added thereto. Next, while keeping the flask contents at 0 to 5 ° C., 0.77 g (8.0 mmol) of lithium trimethylsilanolate was added while stirring to carry out a polymerization reaction, and this was stirred for 20 minutes to stir the contents of the flask. Aged. Next, add 1.0 g of trimethylchlorosilane to the contents of the flask and
After stirring for a minute, the polymerization reaction was stopped. The obtained reaction mixture was washed with water and then tetrahydrofuran was distilled off under reduced pressure to obtain a colorless transparent liquid reaction product (yield: 80
%). As a result of gel permeation chromatography (hereinafter, referred to as GPC) analysis, this reaction product has a number average molecular weight (hereinafter, referred to as
Mn) is 3600, molecular weight distribution [Mn / Mw (M
w: weight average molecular weight, the same hereinafter)] is 1.33. In addition, ²⁹ S of this reaction product
As a result of i-NMR analysis, a trimethylsiloxy group peak was observed at a position of 7.8 ppm. In addition, IR absorption of the reaction product was also measured. ²⁹ Si-NMR
The chart is shown in FIG. 1 and the IR chart is shown in FIG. From the results of the GPC analysis, ²⁹ Si-NMR analysis and IR absorption measurement, it was confirmed that the reaction product was an organosiloxane copolymer represented by the following composition formula. Me [Me ₃ SiO (Me) SiO] ₁₈ (Me ₂ SiO) ₉ SiMe ₃ (wherein Me is a methyl group)

Example 2 The inside of a four-necked flask was replaced with dry nitrogen gas, and 30 g (80 mmol) of cyclotrisiloxane of the formula (2) and 100 g of tetrahydrofuran were added thereto. Next, keep the contents of the flask at 0 to 5 ° C., and stir while stirring.
-Butyllithium hexane solution (n-butyllithium content: 1.6 mol / liter) 0.34 ml (0.54 mmol as n-butyllithium) was added to carry out a polymerization reaction, and this was stirred for 20 minutes. Then, the contents of the flask were aged. Next, 0.1 g of trimethylchlorosilane was added to the contents of the flask and stirred for 50 minutes,
The polymerization reaction was stopped. After n-hexane was added to the obtained reaction mixture and washed with water, tetrahydrofuran and hexane were distilled off under reduced pressure to obtain a colorless and transparent liquid reaction product (yield: 65%). As a result of GPC analysis, this reaction product had an Mn of 54000 and a molecular weight distribution (Mn / Mw).
Was a polymer of 1.38. In addition, as a result of ²⁹ Si-NMR analysis of this reaction product, 7.
A trimethylsiloxy group peak was observed at a position of 8 ppm. In addition, IR absorption of the reaction product was also measured. The IR chart is shown in FIG. GPC analysis as described above, ²⁹
From the results of Si-NMR analysis and IR absorption measurement, it was confirmed that the obtained reaction product was an organosiloxane copolymer represented by the following composition formula. Bu [Me ₃ SiO (Me) SiO] ₂₈₀ (Me ₂ SiO) ₁₄₀ SiMe ₃ (in the formula, Me is a methyl group and Bu is a butyl group)

Example 3 The inside of a four-necked flask was replaced with dry nitrogen gas, and 0.48 g (5.0 mmol) of lithium trimethylsilanolate and 50 g of tetrahydrofuran were added thereto. next,
The content of the flask was kept at 0 to 5 ° C., and 22.2 g of cyclotrisiloxane of the above formula (2) was added to the content while stirring.
(60 mmol) and 13.3 g (60 mmol) of hexamethylcyclotrisiloxane in tetrahydrofuran 1
The solution dissolved in 00 g was added dropwise over 3 hours to carry out a polymerization reaction. This was stirred for 15 minutes to age the contents of the flask. Next, 1.0 g of trimethylchlorosilane was added to the contents of the flask and stirred for 30 minutes to stop the polymerization reaction. The obtained reaction mixture was washed with water, and then tetrahydrofuran was distilled off under reduced pressure to obtain a colorless and transparent liquid reaction product (yield: 85%). This reaction product is G
As a result of PC analysis, Mn was 7,000 and molecular weight distribution (Mn /
It was found to be a polymer with Mw) of 1.31. Moreover, as a result of ²⁹ Si-NMR analysis of this reaction product, a peak of a trimethylsiloxy group was observed at a position of 7.8 ppm. In addition, IR absorption of the reaction product was also measured. The IR chart is shown in FIG. The GPC
From the results of analysis, ²⁹ Si-NMR analysis and IR absorption measurement, it was confirmed that the reaction product was an organosiloxane copolymer represented by the following composition formula. Me [Me ₃ SiO (Me) SiO] ₂₂ (Me ₂ SiO) ₄₆ SiMe ₃ (In the formula, Me is a methyl group)

Example 4 The inside of a four-necked flask was replaced with dry nitrogen gas, to which 30 g (80 mmol) of cyclotrisiloxane of the formula (2), 80 g of toluene and 5 g of dimethyl sulfoxide were added.
Was introduced. Next, the contents of the flask were kept at 0 to 10 ° C., and lithium trimethylsilanolate of 0.
38 g (4.0 mmol) was added, and the content in the flask was aged for 30 minutes while stirring. Next, 40 ml of 0.1 N hydrochloric acid was added to the contents of the flask to obtain 10
The reaction was stopped by stirring for a minute. After the obtained reaction mixture was washed with water, the solvent was distilled off under reduced pressure to obtain a colorless transparent liquid reaction product (yield: 80%). As a result of GPC analysis, this reaction product was found to be a polymer having Mn of 3,600 and a molecular weight distribution [Mn / Mw] of 1.32. Moreover, as a result of ²⁹ Si-NMR analysis of this reaction product, a peak of a trimethylsiloxy group was observed at a position of 7.8 ppm. In addition, IR of the reaction product
Absorption measurement was performed. GPC analysis, ²⁹ Si-NMR
From the results of analysis and IR absorption measurement, it was confirmed that the reaction product obtained was an organosiloxane copolymer represented by the following composition formula. Me [Me ₃ SiO (Me) SiO] ₃₆ (Me ₂ SiO) ₁₈ H (wherein Me is a methyl group)

Example 5 In Example 3, the amount of lithium trimethylsilanolate used was changed from 0.48 g to 1.92 g (20 mmol), and the amount of hexamethylcyclotrisiloxane used was changed from 13.3 g to 66.6 g. A copolymer represented by the following composition formula was obtained in the same manner as in Example 3 except that the content was changed to (0.3 mol). Me [Me ₃ SiO (Me) SiO] ₅ (Me ₂ SiO) ₉₀ SiMe ₃ (wherein Me is a methyl group)

Example 6 The copolymers obtained in Example 1, Example 3 and Example 5,
In addition, a differential thermal analysis (DSC) measurement was performed on an organopolysiloxane represented by the following composition formula for comparison. The results are shown in Table 1 and the DSC chart is shown in FIG. Me (Me ₂ SiO) ₈₅ SiMe ₃ (In the formula, Me is a methyl group)

[0051]

[Table 1] As is clear from the results in Table 1, the copolymer of the present invention is
No melting point peak is observed, and it shows fluidity without solidification from room temperature to low temperature region, and has excellent low temperature characteristics.

[0052]

INDUSTRIAL APPLICABILITY The copolymer of the present invention is a novel compound, is excellent in low-temperature characteristics, heat resistance, temperature-viscosity characteristics and compatibility with various oil agents, and is particularly useful as a raw material for cosmetics, grease and the like.

[Brief description of drawings]

FIG. 1 ²⁹ Si—NM of the copolymer obtained in Example 1.
It is an R chart.

2 is an IR chart of the copolymer obtained in Example 1. FIG.

FIG. 3 is an IR chart of the copolymer obtained in Example 2.

4 is an IR chart of the copolymer obtained in Example 3. FIG.

FIG. 5 is a DSC chart of a copolymer and the like.

[Explanation of symbols]

In FIG. 5, 1 is a DSC diagram of the copolymer obtained in Example 1. 2 is the DSC of the copolymer obtained in Example 3
FIG. 3 is the DS of the copolymer obtained in Example 5
It is a C diagram. 4 is a DSC diagram of an organopolysiloxane for comparison.

Claims (2)

[Claims] 1. The following general formula (1): [In the formula, R ¹ is a monovalent hydrocarbon group, R ² and R ³ are independently a monovalent hydrocarbon group or a halogenated alkyl group, A is a hydrogen atom or the following general formula: —SiR ⁴ (formula R ⁴ is independently a hydrogen atom or a monovalent organic group.
However, at least one R ⁴ is a monovalent organic group), a is an integer of 4 or more, b is an integer of 2 or more, and c is an integer of 0 or more. There is an organosiloxane copolymer represented by 2. The following formula (2): In some cases, the cyclotrisiloxane represented by the following general formula (3): (Wherein R ² and R ³ are independently a monovalent hydrocarbon group or a halogenated alkyl group), together with a cyclotrisiloxane represented by the following general formula (4): R ¹ (R ⁵ R ⁶ SiO) _n Li (4) (In the formula, R ¹ is a monovalent hydrocarbon group, R ⁵ and R ⁶ are independently a monovalent hydrocarbon group or a halogenated alkyl group, and n is an integer of 0 or more.) The ring-opening polymerization is carried out in the presence of a lithium compound represented by the following formula, and then the reaction mixture is treated with an acid or the following general formula (5): XSiR ⁴ (5) (wherein, X is a halogen atom and R ⁴ is independently A hydrogen atom or a monovalent organic group, provided that at least one R ⁴
Is a monovalent organic group), and the method of producing an organosiloxane copolymer according to claim 1, further comprising the step of terminating the ring-opening polymerization by adding an organohalosilane.